WbLS Propotype Studies at CSU (since last Collaboration meeting)

1. WbLSPropotype Studies at CSU (since last Collaboration meeting) • Collimating the x-ray source to verify edge effect on crystal and SiPM (June results) • Results show that observed energy increases with brass collimator, but this is due to brass surface reflection. So all the x-rays are stopping in the crystal, but the light collection depends on geometry and surface reflection. • Reading out P0D scint Bar + WLS fiber + MPPC + CSU preamp with Na22x-ray source (August results) • No x-ray peak in PHA spectrum found using WLS fiber+MPPC. Puzzling? • Offline Studies of backward tracks • Indicate ~30% of CCinc events have a backward track the where the reconstructed 1st layer hit is not the true vertex • Since we are trying to make a live water target, these effects can degrade the hardware improvements. Unfolding techniques studied in n and anti-n data

2. Collimated X-ray Sources (June 2014) • More studies on SiPM’s , CsTl crystal, and Cs137 & Na22 sources • Does the measured E spectrum depend on x-ray source collimation? • This is desired to understand for LAB tests and calibration • Does uncollimated x-rays hits edge of crystal and spread energy? • Ans. is NO, but abs. energy scale increased (dues to brass reflection). This was checked by painting black the brass on the CsTl side. Collimation w/brass plate Source is sitting on top of x-stal Source CsTl 6x6mm2 x-stal SiPM brass

3. Disk sources and Brass plate with fine hole To be used as a simple collimator SiPM with CsTl crystal CsTl crystal, brass plate w/hole +source

4. Na 22 Spectrum on CsTl + SiPM No collimation collimation 511 KeV 1.2 MeV 511 KeV 1.2 MeV Peaks at 31 and 74? Peaks at 37 and 91?? Note the energy Spectrum shifted Up. This is believed To be due to brass Plate reflecting light Back to SiPM

5. Cs 137 Spectrum on CsTl + SiPM No collimation collimation 662 KeV 1.174 MeV b? 662 KeV 1.174 MeV b? Peaks at 50 and 115 Peaks at 39 and 90 Ratio of 511/662=.77 Ratio 31/39=.79 37/50=.74 Fair agreement Higher bumps not understood.

6. P0D Upgrade Detector Update (Aug 18) • HARDWARE • CSU Preamp adapted to Hamamatsu multi-pixel photon counter (MPPC) that couples to WLS fiber. [we are not using the T2K TFB+RMM board readout, instead a PHA] • Preliminary test of MCA+CSU Preamp+MPPC+Fiber+Scint_Bar using Na22 x-ray source • So far no signal peak found with x-ray source, unlike SiPM+CsTl crystal+Na22 source (?) • ANALYSIS • 1) Simulations using NEUT indicate large % of backwards tracks making the vertex position difficult to pinpoint which layer (water or scintillator) has the true vertex. Some unfolding P0Dule by P0Dule being studied Walter Toki, Colorado State University

7. Plans for MPPC+fiber Measurements with WBS Liq. Scint./LAB setup  bar setup Next step is to construct full size prototype (2.2 m long) with WLS fiber+MPPC that is readout by the CSU preamp + multichannel analyzer. Initially we will use a regular P0D triangular bar and test it with x-ray sources Main steps (started on #1) Construct full size triangular bar with WLS fiber set up. Test with x-ray sources at different distances from MPPC using CSU preamp+MCA (see slide 5 and 6 for scope & MCA test). The scint bar and cell walls are OK for x-ray sources Construct full size liquid test cell with WLS fiber. Use conventional liquid scintillator and test with x-ray sources at different distances. Fill liquid test cell with LAB+water mixtures. Test with x-ray sources at different distances. Measure pulse height spectra and compare to 1) & 2) OPEN QUESTIONS Can we find x-ray peak in bars? Set up vertical or horizontal cell for liq.scintor LAB How to hold fiber in fixed position Use acrylic transp. walls (painted?) or Teflon tube w/white walls Seal LAB top with Nitrogen, requires air tight seal w/o-ring? Use fancy o-ring (ultra torr) connectors to get fiber out of test cell. MPPC WLS fiber Prototype cell filled with Liquid Scintillator or LAB+water Conventional P0D triangular scint bar. X-ray Source @511keV Walter Toki, Colorado State University

8. CSU designed fiber connector for MPPC sensor used in T2K connector MPPC Polished Fiber end P0D detector has 11K fiber connectors. Very few problems since 2009 when T2K started running. Walter Toki, Colorado State University

9. Preliminary scope test with CSU preamp and MPPC+fiber in triangular scint. Bar w/x-ray source Mini-coax between MPPC and preamp P0D triangular Scin-tillator bar 2.2m long MultipixelPhoton Counter (MPPC) Connected to WLS Fiber in the scint.bar 511 KeV X-ray source CSU preamp Adapted to Readout MPPC Walter Toki, Colorado State University

10. Average Scope trace of preamp output on triangle bar w/511 KeV x-ray MPPC bias set at 70v X-ray source on bar close to MPPC X-ray source on bar far from MPPC => So x-ray source looks ok on scope with triangular bar and probably for LAB test cell Walter Toki, Colorado State University

11. Multichannel Analyzer + Preamp + MPPC + WLS fiber + P0D scintillator bar + Na22 x-ray No 511 KeV x-ray peak from Na22 source seen in MCA spectrum. This is unlike the SiPM+CsTl+Na22 measurements which had a clear peak??? Note, in T2K, we find a min. ion track that passes through a summed pair of triangular bars (1.7cm) thick, should deposit about 2 MeV/cm (polystyrene) and the T2K P0D detector (in our NIM paper) had 38 p.e./mip/cm. This would imply that a 0.5 MeV x-ray would produce 38/4=9.5 p.e.SO MAYBE I need a higher energy x-ray (1-2 MeV) to find a peak in the MCA??? Without a clear peak from the x-rays, it will be difficult to compare the LAB+water mixtures and different setups. Trya higher energy x-ray source (Co60at 1332KeV or Zn65 at 1115KeV ) to find peak or cosmics??? Or does anyone know where to get a 2 MeV x-ray source to replicate energy deposit of min. ion track? Walter Toki, Colorado State University

12. T2K P0D N.I.M. Paper (used scintillator+WLS fiber+ MPPC readout) Summed for 2 triangular bar energy for min. ion track Min ion tracks in P0D, summing 2 bars This is normalized to 1 cm of path length in the scintillator. Since dE/dx = 2MeV/cm, we expect that 2 MeV yields 38 p.e. And the Na220.5 MeV yields 38/9=9.5 p.e. P0D min. ion track is here Na22 x-ray should be here Walter Toki, Colorado State University

13. Reconstructed “1ST LAYER” Hit Z position and Backwards Track vs True Vertex In T2K analysis, we use the observed “first layer” hit as a vertex. When there is a True vertex with a backwards track, the “first layer” hit is not the same as the True vertex. MC NEUT estimates of this rate are 30%for CCinc and this depends on many factors water-in or water-out run. P0Dule #, Pmand qm, Nu vs. anti-nu data Also it is e backward track rate in bkgds is different from CCincmodes. CCQE seems to be smallest. This is a substantial correction and should have a non-trivial unfolding and syst. error effect on water-in and water-out Measurements. We are investigating unfolding in n and anti-n data P0Dule by P0Dule. See talk by Thomas Campbell for n and anti-n in collab. Meeting. The cross feed appears to be smaller for CCQE. m- We CANNOT easily distinguish between the Two track topologies; scint. vertex or water vertex. Walter Toki, Colorado State University